How can the graph for the rule y equals 2x + 1 be used to predict the result for an input (x value) of 7?

Serena is making an experiment. for that, she needs 20 grams of a 52% solution of salt. she has two large bottles of salt water: one with 40% and the other with 70% of salt in them. how much of each must she use to make the solution she needs? i am in need of